STING‑regulated Ca²⁺–TGF‑β axis drives airway remodeling and lung function decline in asthma: a multi‑omics mechanistic study

Abstract

The progressive lung function decline in severe asthma is poorly explained by traditional inflammation‑centered paradigms. Calcium (Ca²⁺) dysregulation and transforming growth factor‑β (TGF‑β) signaling have been implicated, but the molecular link between them and their upstream regulators remain elusive. We integrated clinical CT imaging, proteomics (6 asthma vs. 6 healthy controls), public transcriptomic data (GSE63142, GSE68479), single‑cell RNA‑sequencing (GSE193816, GSE185048), and functional studies in STING knockout mice and airway epithelial cells. GO and KEGG enrichment, LASSO regression, Spearman correlation, immunohistochemistry, immunofluorescence, co‑immunoprecipitation, western blot, mitochondrial function assays (MitoSOX/JC‑1), Fura‑2 calcium imaging, RNA‑seq and ELISA were used to systematically evaluate the role of the STING‑PPM1F‑Ca²⁺‑TGF‑β axis in asthma airway remodeling. Using logistic regression, we found that disease severity, age, pulmonary function parameters and eosinophil count independently predicted the presence of tracheal cartilage calcification, with the model achieving excellent discrimination (AUC > 0.92). Proteomics identified PPM1F, CAMK2G, MICU2 and CIB1 as key calcium‑metabolism proteins co‑enriched in calcium signaling and TGF‑β pathways; PPM1F expression strongly correlated with reduced FEV₁% ( r = − 0.94, p = 0.005) and recurrent exacerbation risk ( p < 0.01). Functionally, OVA induced time‑dependent mitochondrial ROS elevation and membrane potential dissipation, triggered cytosolic mtDNA release, and activated STING downstream p‑TBK1 signaling. STING activation directly mobilized intracellular Ca²⁺ via both store release and extracellular influx, as demonstrated by Fura‑2 imaging. STING knockout or silencing abolished OVA‑induced PPM1F upregulation and TGF‑β/Smad activation, and attenuated airway pathology. Co‑immunoprecipitation confirmed direct PPM1F‑TGF‑β physical interaction. Single‑cell transcriptomics revealed SFTPC⁺ epithelial cell expansion and high NKX2‑1/FOXA2 activity; multiplex immunofluorescence further identified SCGB1A1⁺SFTPC⁺ double‑positive cells in asthmatic airways, suggesting a potential phenotypic transition of club cells toward an AT2-like state. The STING‑regulated Ca²⁺–TGF‑β axis, activated by mitochondrial stress‑induced mtDNA release, is associated with airway remodeling and lung function decline in asthma. PPM1F is a potential biomarker for asthma severity and recurrent exacerbations; targeting STING or PPM1F may offer new therapeutic strategies for severe asthma. Not applicable.